Method of and apparatus for treating greensand



NOV. 18, 1941'. R, WAGNER ETHOD oF AND APPARATUS FOR TREATING GREENSAND 2 Sheets-Sheet l INVENTOR. RICHARD EJ/MGNER Filed June 8, 1957 ,Lum-011,5 LS' l y ATTORNEYS.

NOV. 18, 941. R, E WAGNER 2,262,785

METHOD OF AND APPARATUS FOR TREATING GREENSAND Filed June' a, 1957 2 sheets-sheet 2 INVENTOR. i En RICHARD E. WAGNER Patented Nov. 18, 1941 UNITED STATES.- PATENT OFFICE.

METHOD OF AND APPARATUSFOR- TREATING AGREENSAND This invention relates to method of and apparatus for treating greensand or glauconite` to improve its Water softening properties and to the improved product, and has for an object the provision of improvements in this art.,

The invention relates particularly to an improved heat treating process for greensand or glauconite.

It has been proposed to heat greensand to improve its qualities as a softener. If the heating is conducted with free exposure to air the greensand Will disintegrate, so it has also been proposed to heat the greensand in a reducing atmosphere. In most cases Warning has been given that the temperature must not exceed 600 C. or the greensand will, be spoiled. In some instances a maximum temperature of 650 C. has been permitted if a reducing atmosphere is maintained. The suggestion made Was to heat the greensand in the presence of heating flames. Practically,

it is difficult to obtain efficient heating up to 650 C. with a reducing flame; so it seems safe to assume that some heating at` the beginning with an oxidizing flame was required. Moreover, in order to obtain the required temperature with a reducing flame and with the usual type of kiln or oven it is necessary to apply heat for a long time, making the process undesirably slow.

Then too, in order to obtain the most immediate effects of the ame it is brought into direct l contact with the greensand. This is objectionable because if even a small portion of the flame is oxidizing it may injure some of the material or reduce its efciency and structural strength as far as water softening purposes are concerned. It also leaves carbon in the greensand.

In some previous processes the greensand has been mixed with oil or other reducing agents in the attempt to avoid oxidizing conditions or to create a reducing atmosphere, but it is obvious y throughout, and moreover, the quality of differgy il.

ent batches is likely to vary greatly.

According to the present invention the greensand is heated to a higher degree and under entirely new conditions from What has ever beforev been proposed for producing a base exchange material, so far as is known. This heat treatment is conducted under carefully controlled conditions to insure that the greensand will no-t be injured. This results in a product which is distinctly superior to any similar product which has heretofore been produced.

A feature of the invention is the heating of the greensand by the indirect application of heat when the heating means involves oxidation as does a fuel flame. It is thus possible to use an oxidizing flame and obtain efficient combustion and a temperature as high as may be desired Without injuring the greensand in any manner. Y

Where electrical heatis cheap it may be used in place of fuel combustion heat and since electrical heat is non-contaminating and in some cases reducing, there is no objection to placing the heating means in the same chamber with the greensand to be heated'. But in any case atmospheric air andoxidizing conditions are substantially excluded.

Another feature of the invention is the application of heat to a thin body vof material whereby every particle may be quickly and uniformly heated. This has many advantagesover heating large bodies of material.

Another feature of the invention is the 'pro- Vision of a continuous operation. Since the material is heated in a thin body it maybe passed along and heated in a continuous stream. This makes for greater uniformity in the product and Very materially speeds up production.

Another feature of this invention is the method and means to heat the greensand rapidly and almost instantaneously to a high temperature and eool'quickly in an oxygen-free atmosphere.

Another feature of this invention is the method andmeans` to heat the greensand rapidly'and almost instantaneously to a high temperature and to cooln quickly in a reducing atmosphere.

Another feature of this invention is the method and means to heatthe greensand to a high temperature and maintain a non-oxidizing or reducing atmosphere v Without adding reducing agents.

Another feature of this invention is the method and means to heat greensand to a high temperature and maintain a non-oxidizing or reducing atmosphere due to the natural agents present in the greensand itself.

Another feature of the invention is the method and means for protecting the highly heated rgreensand by the vapor of occluded or combined Water driven off from the greensand.

Another feature of the invention is the method to a high temperature under the specied env vironment but which will not be injured materially or destroyed under such conditions.

Another feature of the invention is the method and means for hydrating the heat-treated greensand and .the ability of the heat-treated greensand to withstand this treatment to produce an improved nal product. 1

`Another feature of the invention is the method and means for hydrating the heat-treated greensand with an acid or an alkali or both and the ability of the heat-treated greensand to withstand this treatment to Aproduce an improved nal product. Y Another feature of the invention is the irnproved nal product and its ability to withstand regeneration with either salts or acids whereby a greater range of base-exchange reactions may be efficiently performed by the greensand.

yOther objects and features will be apparent to those skilled in the art from the following description of an exemplary embodiment of the invention.

- In order to illustrate the principles of the invention one specific embodiment will be described in detail, reference being made to the accompanying drawings wherein: Fig. 1 is an elevational View of a plant embodying the invention; Fig, 2 is a verticalsection at the feeding end ofthe apparatus, theview being taken on the 'line 242 of Fig. 1;

Fig. 3 is a vertical section through the-furnace, the view being taken on the line 3-3 of'. Fig.' 1;

Fig. 4 is a vertical section at the discharge end of the heating drum, the view being taken on'the line 4-4 of Fig. 1; and

Fig'. 5 is a vertical section at the discharge end of the hydrating drum. the view being taken on theline 5--5 of Fig. 1.

In carrying out this process with the apparatus shown, greensand is preliminarily washed and lclassified to remove fines, clayey inclusions and coarse particles and is then dried until most of the adhering dampness is driven off. The remaining particles are composed principally of glauconite but contain some clayey matter, some iron sulphide, free silica and other substances. Y l'lhejdried greensand is elevated by any suitablemeans and dropped into a feed hopper I 0 provided with an adjustable spout II to deposit the greensand in a feed or pick-up trough I2. By adjusting the vertical position of the slidable spout sleeve Ila the height of the body of sand I3 in `the trough l2 may be varied to vary the amount of feed as will be explained presently. Means are provided for passing the greensand ina thin body or layer through a heating zone without coming in contact with the heating medium or harmful gases of fuel combustion and oxidizing media, to quickly heat it to any desired temperature and to cool it, before coming in contact with air, to a point where air will have no harmful eect upon it.

The means herein shown for this purpose comprise an inclined rotary ldrum I6 mounted on trunnions Il and rotated through gears I8 and I 9 by a shaft 20 driven by a motor MI.

Vflame may be made as oxidizing as desired to create any temperature required. None of the combustion gases come in contact with the greensand being treated.

The portion of the drum within the furnace which is highly heated may be made of a metal which is highly resistant to heat without losing its shape or deteriorating under the conditions to which it is subjected. For example a 28% chromium steel may be used. A cast special alloy steel has been found most suitable for the very high temperatures which are preferred. The portions lBa, |617V of the drum which extend outside the furnace walls may be formed of a lower quality metal. They may be joined to the Gentral portion by-flanges |60 which preferably include heat insulating material such as asbestos to reduce the heat passing from the central portionto the end portions.

yIn order to completely exclude air from thek interior of the drum both ends are closed by suitable heads. The upper head 16d may -be pro-l vided with a small opening `25 to permit such gases as are generated in the drum'to escape. The entire vupper end of the drum maybe enclosed by a hood 28 evacuated through a pipe 29` by a gas pump P operated by a motor M2. The gases are discharged from the pump throughr adischargepipe 30. v i -v Material is fed into the drum i6 by a curved feed pipe -or scoop 3l secured to and rotating with the drum. The height of the sand inthe trough l2 determines the length of arc along which the feed pipe engages the sand and hencethe amount of sand tation of the drum. Y

The greensand passes as a thin stream down the drum as it rotates due to the pitch or mechanical feeding means of the drum. During this passage the greensand is rapidly heated unwhich is fed in at each rotil near the end'of the furnace for approximately very short, say ve or ten minutes. The heating is thus seen to be very rapid. Y Y

The gases generated by heating the greensand may include steamfrom the moisture and water of occlusion or composition driven off, and sul- The time of passagey through the entire heating zone or furnace is for market.

treatment or both may beA employed.

"phurfpossibly in some combined form,y from'the iron sulphides contained in the greensand. These gases will insure that non-oxidizing or reducing conditions will exist withinsthe drum.

4"The-treated greensand is rapidly-cooled in the .end portion VIb of the druml" If the cooling of l' the drum by air is not suflicientlyrapid the drum may be further cooled by streams' of waterfrom a -pipe 32 or otherwisef The heat-treated greensand is not exposed to the air until it has cooled t sufficiently to be unharmed when sofexposed.

V`The relatively cool greensand'- is` discharged from the drum by a helicalf'dischagre pipef33 f secured to and rotating with"the-fdrum.y rIAhe pipe 33 opens into one lside ofl the' lower end of the drum so that a quantity? of greensand enters it Lat every turn.V` The-successive" charges" of `Agreensand form air seals in the4 lower loops of the v'coiled pipe'33 to `positively exclude air from the drum. y The heat-treated greensand may'beused irnacteristics. simply by the-use of the greensand'in a water 'softener'f'but it has been found thatby combin- 'ing other treatment ywith the 'hydration' the greensand is-improved and made more suitable An alkali After the greensand has cooled sufficiently it may be transferredv in any desired manner, as by conveyor, vehicle or blower to bins or other places of storage, shipment or further treatment. For

further discussion, it will be assumed that it is carried to a hydration device. As shown herein, the greensand is nally discharged from the end of the pipe 33 into a hopper 34 leading into the Waste gas discharge pipe 3U previously mentioned. An adjustable baille plate 35 in the pipe causes the gases to pass without escaping to any extent and to create a suction on the injector principle to entrainv the same with the gases. The time of passage from the pipe 33 to the hopper 34 is very brief and the gases in the pipe 3D are non-oxidizing in nature so the greensand is not oxidized even if fairly hot. If desired, an air excluding hood may be placed around the discharging greensand. It is to be understood that if the greensand is properly protected from treatment or'an acid 'fior-'its ultimateuse J'I'henagain, it is generally 1. assumed thatzthe Vexchange capacity! of a zeolite to I'arilarge :extent isl due to its surface area;` that is,lby1-increasing the surface area the exchange 'capacity is increased'. Because of the heat treatment employed above, it is possible with various @methods to increase-- the surfacearea of the greensand. For example,byv subjecting the greensand which has been treated according to thefpresent processl with caustic soda the green- -`salnd?will-not only become hydrated but at the .same time the caustic will remove silica and alumina without weakening the grain structure,

thereby-increasing"the 'surface area so that the -'-exchange-capacity of this material can-be-inycreased E100% over that'of the raw greensand otherwise processed for waterv softening purposes.

Materials produced on a commercial scale ac- Jcrding' to @the-i present invention consistently V-fshow arr-increase in porosity, since the finished product-on a dry basis-weighs only-78 pounds per cubic-'foot against 90 pounds per cubic foot for the raw dry greensand. This increase in porositycanbest be accounted for by the expandingaction of the Water of combination contained within the greensand molecule when` subjected to a high temperature and a short heating period;

while the increase in hardness of the grains is undoubtedly due to a simultaneous sintering ac- Mtion. The use of caustic nforhydraticn or rehydration isywell knownbut due tothe particuj llar-"-preetreatment "employed, herein, special advan-tages are obtained.

In a similar manner, the greensand which has undergone the heat treating process described above can be hydrated or treated with an -acid which instead of removing silica and alumina by means of caustic will remove iron and other matterV soluble in acids, thereby increasing the air it may be transferred at a higher temperature than it would if exposed to air.

The heat-treated greensand is hydrated in any suitable manner. For example, it may be blown through the pipe 30 into a hopper 38 and thence fed into a hydrator 39.

Hydration may be effected in the hydrator by water, preferably heated, by acids such as hydrouoric acid or phosphoric acid, by alkalis such as caustic soda, or other suitable substances. The substance selected will be the one which is most appropriate for the results to be achieved. y

If hydration alone is desired, water is adequate, if iron is to be removed suitable acids may be used; if silica or aluminum or both are to be removed alkalis such as caustic soda or acidsl surface area and the exchange "capacity, Such acid treated material can or may be used on waters of different character and for obtaining different results. While sodium chloride is generally used for regenerating zeolites, the abovetreated material can be regenerated with alkalis or acids to form alkaline or acid zeolites for various purposes.

Assuming that caustic soda is used in thehydrator, the greensand which has been heat-treated according to this process will withstand the action of a much higher concentration of caustic solution without disintegrating than will v greensand made by previous processes.

The greensand from the hopper 38 is blown or otherwise conducted into the liquid bath of caustic soda or other hydrating material in the hydrator. The bath is preferably kept heated, say at about 230 F. or boiling in any suitable manner as by blowing live steam into the bath by a pipe 40. 'I'he hydrator drum is constantly rotated to keep the greensand and liquid thoroughly mixed together. The greensand may remain in the hydrator about one hour on an average. Additional caustic or caustic solution may be added as desired, while the apparatus continues in operation, through a feed device 45.

Instead of or in addition to heating the bath by steam it may be heated by an oil burner 4l,

the drum being suitably enclosed in furnace walls vention.

elevate thegreensand and dropjit into ahopper 43 leadingtoa chute ML@` By adjusting the axial position of the' hopper` 43 in the drumit is made to intercept moreor less `of the length of the buckets v:l2 and hencegmore or less ofthe-material discharged from the buckets. A v i YSome liquid will be removed With. the sand f but this may .latergvbe washed out and the sand subsequently dried. y

By operating the -heat treating device tov deliver al constant quantityj of ltreated greensand of uniform quality, it is-made practicable to operate the hydrator continuously. f

lits ofthe prior art and the scope of the subn joined claims.

I claim: 1. TheY process of treating greensand to improve it for base exchange reactions which comprises, subjecting the greensand in Va thin body to a temperature 'of 950 C. or above for a short period of 5to 10 minutes in a closed -chamber in an inert or reducing environment produced from the greensand itself free from air and combustion-.names and gases, and then quickly cooling thegreensand free from air and combustion No attemptvvill be `made to explain the thev ory underlyingthe reactions which occur during theprocess., The steps of the processhave been explained with sufcient'particularity to enable a person skilled in the artto practice the in- So it is believedl sulcient to statethat the material produced has been found superior to any other known for generalwater softening purposes.' It is quite lblack-in color` instead of green likeV most greensands; Vand is harder and Will withstand the disintegrating'action in softening apparatus without Vbreaking up or -sludging vbetter than any other.knovvngreensand,` or any .i zeolite at all whether natural orarticial, for

that matter. .Y

While one embodiment of .the -invention has been described in considerable detail to furnish a clear understandingof the principles of the invention it is to be. understood that the invention may be variously embodied within the limlames and gases. Y

Y l 2. `"Iheprocess of treating greensand to improvev it for base exchange reactions which comprises, subjecting the'greensandpin a thin body to a temperature of 950 C. or above for a short quickly, and blowing the greensand to` a hydration chamber by gases withdrawn from the heating chamber. f

- RICHARD E. WAGNER. 

